The present invention relates to video quality test and measurement products, and more particularly to a fast video temporal alignment estimation for aligning distorted and corresponding source videos.
Capturing of video encoding and transmission distortions is fundamental to video quality test and measurement products. In applications requiring accurate assessment of video quality, it is required that video distortions be measured by comparing a distorted video against the corresponding source of the video. One necessary requirement for such comparison to be made is that the distorted and source videos be perfectly aligned spatially and temporally. Typically the misalignment estimation is computationally costly as misalignments are detected by searching both a spatial and temporal match simultaneously in a three dimensional space, two spatial dimensions and one temporal. Due to the computational load most video quality test and measurement products operate in non-realtime.
What is desired is a fast video temporal alignment estimation method in order to perform video quality measurements accurately in realtime.
Accordingly the present invention provides a fast video temporal alignment estimation method that is able to resolve temporal alignment independently without requiring the existence of a scene break or fast motion. A distorted video and its corresponding source video are both transformed into signature curves. A cross-correlation between consecutive frames in the video generates a data point for the signature curve, the accumulation of the data points for a video forming the signature curve for the video. Then the two signature curves are matched using a normalized cross-correlation technique, the maximum value of the cross-correlation indicating that the videos are aligned. After the temporal alignment then spatial alignment may be performed using any fast spatial alignment algorithm. The spatially and temporally aligned videos may then be processed by an appropriate instrument for video quality measurements.